Controlled range and payload for unmanned vehicles, and associated systems and methods

ABSTRACT

The presently disclosed technology is directed generally to unmanned vehicle systems and methods configured to satisfy a first set of export control regulations, such as those within the jurisdiction of one government entity or international body (e.g., the U.S. Department of Commerce) without falling within the purview of a second set of export control regulations, such as export control regulations within the jurisdiction of another government entity or international body (e.g., the U.S. Department of State). Through limited range of operation, limited payload types, limited capabilities, and tamper-proof or tamper-resistant features, embodiments of the unmanned vehicle system are designed to fall within the purview and under control of one agency and not within the purview and under control of another agency.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of International PatentApplication No. PCT/US12/65360, filed Nov. 15, 2012, entitled CONTROLLEDRANGE AND PAYLOAD FOR UNMANNED VEHICLES, AND ASSOCIATED SYSTEMS ANDMETHODS, which claims the benefit of U.S. Provisional Patent ApplicationNo. 61/560,234, filed Nov. 15, 2011, entitled CONTROLLED RANGE ANDPAYLOAD FOR UNMANNED VEHICLES, AND ASSOCIATED SYSTEMS AND METHODS, eachof which is incorporated by reference in its entirety. To the extent theforegoing application or any other material incorporated herein byreference conflict with the present disclosure, the present disclosurecontrols.

BACKGROUND

Unmanned systems (e.g., unmanned aerial or aircraft systems, unmannedground systems, unmanned underwater systems) provide a low-cost andlow-risk alternative to a variety of reconnaissance-type tasks performedby manned systems. Unmanned aircraft systems, for example, are used byTV news stations, by the film/television industry, the oil industry, formaritime traffic monitoring, border/shore patrol, civil disastersurveillance, drug enforcement activities, monitoring fleets of fish(e.g., tuna), etc. Law enforcement agencies use manned helicopters andairplanes as an integral part of their operations, but unmanned aircraftsystems are starting to be used in a growing number of places. The usesfor aviation equipment in law enforcement that can be filled by unmannedaerial systems include, for example:

-   -   Photographic uses,    -   Surveillance uses,    -   Routine patrol/support,    -   Fugitive searches,    -   Search and Rescue,    -   Pilot Training,    -   Drug Location/Interdiction,    -   SWAT operations, and    -   Firefighting/Support.

Table 1 provides statistics related to the use of aviation units bylarge law enforcement agencies with one hundred or more full timeofficers in the United States.

TABLE 1 Aviation Law Enforcement Statistics Number of aviation units, US2010 Rotary - median $/flt.hr. $168 $45 (Fuel) (Maintenance) Fixed -median $/flt.hr.  $54 $74 (Fuel) (Maintenance) Unmanned $1.79/hour

Unmanned systems can include a Global Positioning System (GPS) receiverto obtain adequate near real time position data to know where the systemis, and calculate attitude with feedback information from solid-staterate gyros. Unmanned aerial systems capable of, for example, automatedtake-off/launch, flight via programmed way-points, and snag-typerecovery have been developed that reduce the cost to own and operatewhen compared to human-operated aircraft (e.g., single-pilot fixed androtor aircraft). Unmanned vehicles that are covered by the United StatesMunitions List (USML) are subject to export controls administered by theU.S. Department of State under the Arms Export Control Act and theInternational Traffic in Arms Regulations (ITAR) defined at 22 C.F.R.§§120-130. For example, the Missile Technology Control Regime (“MTCR”)(See 22 C.F.R. §121.16) defines two categories of unmanned air vehiclessubject to State Department Control, each category subject to differentexport controls. “MTCR Category I” vehicles are those vehicles that 1)are capable of at least 300 km of autonomous flight and navigation and2) can carry a payload of at least 500 kg. “MTCR Category II” vehiclesare those vehicles that either 1) are capable of at least 300 km ofautonomous flight and navigation or 2) can carry a payload of at least500 kg. (See 22 C.F.R. §121.16 (2011).) Commodities subject to exportcontrols administered by other agencies (e.g., the U.S. Department ofCommerce), such as unmanned air vehicles that are incapable ofautonomous flight and navigation for 300 km or more and cannot carry apayload of 500 kg or more, are subject to less stringent exportrequirements.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating a control station configured inaccordance with an embodiment of the disclosure.

FIG. 2 is a block diagram illustrating subsystems of an unmanned aerialvehicle configured in accordance with an embodiment of the disclosure.

FIG. 3 is a block diagram showing some of the components incorporated inassociated computing systems in accordance with an embodiment of thedisclosure.

FIG. 4 is a flow diagram illustrating the processing of an “operatevehicle module” configured in accordance with particular embodiments ofthe disclosure.

FIGS. 5A-5B illustrate overall views of apparatuses and methods forcapturing unmanned aircraft in accordance with an embodiment of thedisclosure.

FIGS. 6A-6C illustrate an arrangement for launching an unmanned aircraftin accordance with an embodiment of the disclosure.

DETAILED DESCRIPTION

The presently disclosed technology is directed generally to unmannedvehicle systems and methods configured to satisfy certain restrictions.For example, the systems and methods can satisfy Commerce Departmentjurisdiction requirements without falling within the purview of StateDepartment control. Through limited range of operation, limited payloadtypes (e.g., surveillance equipment, munitions, insecticides or othermaterials for agricultural crops) and capabilities, and tamper-proof ortamper-resistant features, embodiments of the unmanned vehicle systemare designed to fall within the purview and under control a first set ofexport control regulations or requirements, such as ExportAdministration Regulations (“EAR”) overseen by the U.S. CommerceDepartment, and not within the purview and under control of a second setof export control regulations or requirements, such as MTCR, ITAR, andother State Department control thresholds. Disclosed techniques inaccordance with particular embodiments provide protection againstrepurposing a vehicle as a weapons delivery device and repurposing acommercial vehicle for military or other operations by, for example,modifying operation of the vehicle (e.g., preventing vehicle systemsfrom executing, preventing the vehicle from launching, preventing thevehicle's engine from starting) in response to detecting theseconditions. Representative techniques can also provide protectionagainst in-flight handoff between ground controlling authorities,eavesdropping of available data streams, and so on by, for example,restricting use of commands for performing these functions. Althoughthis disclosure discloses particular embodiments in the context ofCategory II vehicles by way of example, one skilled in the art willrecognize that the disclosed techniques may be applied to Category Ivehicles in addition to other vehicles or commodities that may besubject to varying sets of requirements.

I. System Design and Capabilities

In some embodiments, the unmanned vehicle has a low payload capabilityof 3.3 lbs., (1.5 Kg), a diameter of 7 inches, a length of 42 inches, awingspan of 10 feet, an empty weight of 26 lbs, and a gross takeoffweight of 40 lbs. Furthermore, the unmanned vehicle's design andcapabilities are based on its airframe structure electronics systems andsoftware architecture, which includes trusted computing technologies,and are described in further detail below.

A. Airframe Structure

In certain embodiments, the aircraft structure, which comprises thefuselage, main wing box, wing skin sandwich panels, winglets, fuel tank,and internal brackets, is fabricated using, for example, low cost carbonfiber/epoxy materials, fiberglass, aluminum, or molded plastics based onconsiderations of size, weight, power, cost, etc. and hard-tool moldingcommercial techniques. Such techniques have been used in, for example,bicycle frame, snow-sport and water-sport equipment manufacturing.

B. Command and Control System and Software

1. Command and Control System

In certain embodiments, the electronic hardware and software of theunmanned vehicle are configured to limit range (distance from designatedpoint, such as a point of origin or launch location), but notnecessarily endurance (total distance traveled during a flight). Forexample, the range can be limited to 60 nautical miles from the operatorcontrol station (e.g., ground control base station or mobile controlbase station) using a radio transmitter and antenna gain combinationthat limits the maximum physical range of communication for the providedradio link on the aircraft to the control station antenna. Flightoperation limits can be achieved through the physical limits of radiofrequency command and control wireless data links coupled with softwarecommands that prevent waypoint entry beyond the radial distance of 60nautical miles. For example, aircraft mission management software can beconfigured to compare control station GPS location to aircraft GPSlocation to maintain radio-link margin distance at all times. In thecase of a lost data or communication link, the aircraft can alter courseto regain the lost data or communication link with a control station. Iflink interruption continues, the aircraft can return to the last knownGPS position of the control station to execute flight termination oremergency landing procedures. In this embodiment, travel of the unmannedvehicle beyond 60 nautical miles causes the auto pilot to steer theunmanned vehicle toward the control station GPS location to securecommunication. The software may also be configured to limit the range ofthe unmanned vehicle or return to base at or below the 299 km distancefrom a launch location to meet MTCR requirements.

a. Navigation System

In some embodiments, to limit the operation of the unmanned vehicle, theunmanned vehicle is not equipped with a magnetic compass oraccelerometers to estimate current altitude, speed, and direction.Instead, the unmanned vehicle can be equipped with a rudimentarynavigation system. Without adequate GPS data, the unmanned vehiclecannot maintain a known navigation solution and will attempt to returnto the control station or terminate travel based on one or moreemergency procedure protocols known to those of ordinary skill in theart. For example, in the case of lost communications and/or lost GPSconnectivity, the unmanned vehicle can deploy speed-reducing devices(e.g., parachutes or parafoils) and/or airbags and execute a spin-stallmaneuver, causing the aircraft to tumble as slowly as possible to theground. The unmanned vehicle's navigation protocol and emergencyprocedures are designed to prevent flight beyond the 60 nautical milerange of the Command and Control system. The unmanned vehicle maytypically fly over uninhabited terrain at altitudes below 5,000 feetabove the ground, thereby reducing the probability of human injury. Theunmanned vehicle can be configured to tumble out of the sky usingautomatic auto rotation and/or automatic chute deployment in the case oflost communications and/or lost GPS connectivity.

In other embodiments, a collection of multiple control stations areavailable for communication with the unmanned vehicle system. Forexample, environment conditions (e.g., obstructions to line of sight)and communication systems may prevent the unmanned vehicle system fromcommunicating with control stations beyond a certain distance, such as60 nautical miles. In these embodiments, control stations and theunmanned vehicle system can perform a handoff procedure as the unmannedvehicle system approaches a specified distance (e.g., 60 nautical miles)from the control station with which the unmanned vehicle system iscommunicating to another control station so that the unmanned vehiclesystem can maintain control station connectivity and take advantage of agreater permissible range, such as 299 km from a launch location. Thehandoff procedure may be based on, for example, the type of vehicle andcontrol station involved, the speed and/or direction of the vehicleand/or control station, the launch location or target of the vehicle,and so on. In this manner, the range of the unmanned vehicle canapproach the “299 km from launch location” limit discussed above.However, embodiments of the system will prevent the aircraft from flyingbeyond the “299 km from launch location” limit discussed above.Furthermore, the aircraft can be configured to set a transponder tosquawk an emergency code if the aircraft is approaching the edge of anavigation restriction zone or is within a predetermined distance (e.g.,ten feet, 2000 feet, or one mile) from the edge.

In some embodiments, the unmanned vehicle system is configured toprevent flight beyond 60 nautical miles from the control station (e.g.,ground control station) and/or 299 km from a launch location at least inpart by:

-   -   establishing and confirming location of the Control Station,    -   maintaining an autopilot navigation solution without a GPS        solution and switching to an Emergency Response Procedure, such        as changing course to “dead reckon” toward the control station,        maintaining level flight until a flight termination timer        expires, executing a spin-stall maneuver to slowly descend from        the sky, or establishing a GPS-based navigation solution,    -   limiting the Command & Control Data Link RF communication        between the aircraft radio transmitter and the associated        send/receive antenna for the control station. In the event that        communication is lost, the unmanned vehicle will attempt to        navigate toward the last known GPS coordinate location of the        control station to achieve connection. If connection is not        re-established, the unmanned vehicle will automatically navigate        back to a predefined GPS location within 3 nautical miles of the        control station for emergency landing.    -   Hard coded data entry configured to:        -   control emergency landing location to within, for example, 3            nautical miles of the control station,        -   prevent “hand-off” to alternate control stations, and        -   prevent way-point entry beyond a 60 nautical mile radius of            the GPS coordinates for the control station.

b. Control Station and Unmanned Vehicle

In some embodiments, the control station and unmanned vehicle comprisecomputers, video monitors, hobby-market controllers for radio controlledhobby vehicles, keyboards, track-ball mouse, power cables and connectorsand associated software.

In some embodiments, the control station and unmanned vehicle utilizeTrusted Computing Group technologies modeled after implementationsdeveloped under the NSA High Assurance Platform (HAP) Program (seehttp://www.nsa.gov/ia/programs/h_a_p/index.shtml). The unmanned vehiclecan use Trusted Platform Module (TPM) security chips, such as thoseprovided by Infineon Technologies AG, that attest to or confirm theidentity of the control station and the aircraft computer's identity andfurther confirm the integrity of the software running on each.Furthermore, computers within the unmanned vehicle system can use, forexample, a National Institute of Standards and Technology (NIST)verified Trusted Operating System utilizing Trusted Boot to measure andattest to the boot measurements (e.g., system configuration measurementsand diagnostics made at boot time) when appropriate. Remote confirmationverifies software state on client and remote machines. Trusted Computingtechnologies confirm that the unmanned vehicle is operating as expectedbased on its design (e.g., only authorized software is running on thevehicle) to ensure that the unmanned vehicle system remains compliantwith Commerce Department export control requirements.

Trusted Computing technologies allow the unmanned vehicle to verify theintegrity of sub-system components relative to initial configurationinformation. For example, at boot-time or during operation, a trustedcomponent of the unmanned vehicle can verify that the unmanned vehicleis configured as originally designed by querying the various componentsfor their identification and current configuration information. In thismanner, the unmanned vehicle can ensure that it is equipped withcomponents that do not render the unmanned vehicle subject to StateDepartment export control. For example, system devices (avionics,radios, transponder, integrated flight controller, ground controlstation, etc.) are configured to include a software module and/or ahardware module that can publish an identification of that device andcan certify identifications from some other device. In other words, onecannot, for example, swap in military mission components subject to ITARcontrol without causing system failures and rendering the systeminoperable because the swapped-in components will have differentidentifications than the components of the vehicle in its initialconfiguration and the vehicle will not be permitted to, for example,operate, launch, accept input commands, transmit data, etc. Accordingly,an unmanned vehicle constructed and equipped to comply with CommerceDepartment export control requirements can be rendered inoperable aftermodification. In some embodiments, the unmanned vehicle may send acommunication to a ground control station or satellite in response todetermining that its configuration has changed.

In some embodiments, the unmanned vehicle includes a commercial AdvancedEncryption Standard (AES)-256 Encrypted data interface in the onboardelectronics and all data links between the unmanned vehicle and thecontrol station. Encrypted data protocols will allow operators tomaintain configuration control and limit device connection with specificencryption keys controlled by a central authority.

c. Tampering Prevention

In some embodiments, the hardware and software of the unmanned vehiclesystem are designed to prevent and/or detect tampering and providesecurity to the system. Trusted Platform Module (TPM) technology to beused in the unmanned vehicle system (e.g., Infineon Technologies, TPMChip SLB9635T1.2, ECCN 5A992, TPM Professional Package (Software), ECCN5D002) is controlled by the Commerce Department. In some embodiments,the unmanned vehicle may send a communication to a ground controlstation or satellite in response to detecting tampering. Design elementsinclude, for example:

-   -   An Avionics Module containing: a) the commercial GPS receiver        (e.g., Novetel OEMV-2-L1L2 GPS-ECCN No. 7A994); b) an Auto Pilot        computer; and c) a regulated power conditioning system. These        components can be factory sealed in the Avionics Module to        prevent tampering. Data communication to and from the Avionics        Module requires matching encryption keys to function. The        avionics are factory—programmed using specific compiled code and        Trusted Platform Module encryption techniques.    -   The Avionics Module is capable of factory-only programming and        encryption key configuration. Updates to the software are        limited to factory only upgrades of the Avionics Module.    -   For an unmanned aircraft, a tail-less design prevents        over-flight weight or aircraft length modifications due to the        physical limitation of flight envelope (Bernoulli principle).        Without proper updates to the autopilot, stable flight is        typically impossible within 30 seconds to 2 minutes. The time        elapsed between stable and non-stable flight will depend on        localized atmospherics, how much integration error the aircraft        attitude algorithm has accumulated at the time the GPS is turned        off, and the actual maneuver the aircraft is performing at the        moment the GPS is turned off. For example, navigation direction        is lost immediately when the aircraft does not have an on-board        compass and GPS provides the only reference to Earth.

Sensors for the unmanned vehicle may include, for example, EAR99 (i.e.,subject to Commerce Department export control) Electro-optical sensorsto a commercial Sony Handycam®, LongWave Infrared Sensors, such as theGoodrich Aerospace Short Wave Infrared (SWIR).

2. Software

In some embodiments, the software of the unmanned vehicle system iswritten using C++ industry standard commercial language and developmentmethodology. A modular system architecture allows feature sets of thevehicle control or control station software to be removed beforecompiling at the factory. Removal of features sets for the softwareassures the system operation is limited to the desired feature set. Thefeature set specific to the unmanned vehicle will be modules that areleft out or added in when code is compiled and no source code orvariable settings/switches will be available to the user. Moreover,human-readable characters may be removed from the code using, forexample, a pre-parser. Further, the code may be subjected to obfuscationtechniques or programs (See, e.g.,www.preemptive.com/products/dotfuscator/overview).

In some embodiments, delivered unmanned vehicle hardware does notinclude programmable devices. Software and hardware upgrades to theunmanned vehicle are accomplished by delivering new hardware from thefactory. Software and hardware features are limited to factory deliveredconfiguration through the use of Trusted Computing technologies.

The control station hardware includes commercial off-the-shelf workstations and laptops using, for example, the MICROSOFT WINDOWS®operating system, which is recognized by industry as a trusted operatingsystem allowing complete implementation of the Trusted Computingstrategy applied to the unmanned vehicle system.

3. Representative Design Features:

Table 2 below identifies representative design features for severalsubsystems of an aircraft system configured in accordance withembodiments of the present technology.

TABLE 2 Navigation: Range Restriction - Prevent vehicle from flyingoutside of a Latitude/Longitude box and ROM Chip prevent user frommodifying the Latitude/Longitude box by, for example, burning theLatitude/Longitude box into a ROM chip. Range Restriction - Preventvehicle from flying outside of an expandable Expanding BoxLatitude/Longitude box and prevent user from modifying theLatitude/Longitude box beyond a certain size. Reduced Navigation Limitthe accuracy of the navigation system. Accuracy Flight TerminationDisable navigation system if vehicle exceeds a predetermined speed. onHigh Speed Limited Speed Prevent indicated airspeed from exceeding adefined threshold. Server-Validated Software validates flight commands(flight plans, orbits, and recovery Flight Plans definitions) through ahome server. The data is sent to the server, if it passes a given set ofcriteria it is encrypted with a Private Key and returned, requiringdecryption with, for example, a public key. Approved Flight Box Acombination of the Latitude/Longitude box restriction and thePublic/Private Key challenge and response. Time Limited A combination ofany of the Pub/Private key schemes, but the Approvals response has atime limit encoded into it. After the time limit (Expiration) expires,it will no longer be accepted. Minimum Height Software will not commandflight less than a predetermined altitude Above Terrain above the groundlevel (e.g., 200 ft) as reported by Digital Terrain Elevation Data(DTED). Flight Termination Command a flight termination at currentlocation if engine is not on Engine Out running. Flight Termination Acombination of the DTED restriction and the engine out flight on LowAltitude termination. Homecoming -- Near Prevent a change to the homecoming route if the terminal point is Launch Location more than apredetermined distance from the launch location (e.g., 50 nauticalmiles). COMMUNICATION: Unique Radios Use radios which are not compatiblewith radios used in a vehicle subject to ITAR control (or otherregulations). PAYLOADS: Payload Weight Prevent operation if mass andcenter of gravity change. Restrictions Video to Fly Prevent operation ifproper video signal is not detected because, for example, a videorecorder has been removed. DECODING/DATA ASSURANCE: Potting SimplifiedThe entire avionics unit is converted to single board and then potted,Avionics so as to make it impossible to add/remove/decode/modify anyparts to unit. Anti-Tamper -- Any attempt to disassemble a section ofthe vehicle breaks it. Avionics Frangible connectors. Anti-tamper --Elec Any attempt to disassemble a section of the vehicle breaks it.Discharge Charged capacitors that discharge into ICs if not openedcorrectly. No Payload -- Foam Empty spaces in the vehicle are filledwith unremovable foam/goo (so Fill there is no place to add explosives).Removed Screens Screens deemed unnecessary are hidden. SingleProgramming -- Prevent reprogramming of executables/param files in thefield (e.g., All burn once NVRAM). HARDWARE/SYSTEM INTEGRITY:Proprietary Use proprietary (or difficult-to-find/acquire) connectors tomake it Connectors difficult to add/swap part. Anti-Tamper -- Usehardware that prevents user from reading NVRAM/FLASH data UnreadableFLASH (e.g., MPC-555).

C. General Electronics

In some embodiments, electronics used in the unmanned vehicle systeminclude those derived from U.S. industrial and automotive gradecomponents. For example, an auto-pilot system of the unmanned vehiclemay include the Motorola/Freescale 555 processor, a widely usedmicroprocessor in the automotive industry.

1. Circuit Cards

Circuit cards of the unmanned vehicle system can be designed by usingIPC standard design and manufacturing standards commonly applied by theU.S. industry.

2. Propulsion System

The propulsion system of the unmanned vehicle can be based onpublicly-available hobby aircraft 2-stroke technology (e.g., available3W-Modellmotoren GmbH (3W Modern Motors) of Rodermark, Germany),commercially-available electric motor systems, commercially-availablebattery and/or fuel cell technologies, etc.

3. Generator

The electrical power system (e.g., the generator) of the unmannedvehicle can include, for example, a brushless electric motor, such as aKollmorgen industrial brushless electric motor (EAR99) available fromKollmorgen of Radford, Va. or a Kollmorgen authorized distributor.

II. Export Control Analysis

MTCR & ITAR

The disclosed unmanned vehicle is designed with limited capability sothat it will not meet ITAR-control threshold criteria (e.g., range equalto or greater than 300 km), thereby not reaching the minimum thresholdfor State Department export control, thereby falling within the purviewof and under control of the U.S. Commerce Department export controlregulations.

As described in Section I, specific safeguards have been put in place toprotect concerns of National Security and U.S. government militarytechnologies. In particular embodiments, such safeguards, which weredescribed in more detail in Section I, include:

-   -   Range Limited to less than 300 Km—The software and hardware will        limit flight range to less than 300 Km from point of origin.    -   Trusted Computing Technologies—Tamper-proof and/or        tamper-resistant technologies (endorsed by NIST) to maintain the        as-delivered configuration of the unmanned vehicle and control        station.    -   Commerce Controlled Components—Components of the unmanned        vehicle and control station are traced to EAR control        requirements (Commerce Depart export control).    -   Aircraft Limited Payload Capacity—The design and configuration        of the aircraft limit payload capacity to less than 2 kilograms        in particular embodiments.

One feature of embodiments of the present technology is that byconstructing the unmanned vehicle without ITAR-controlled components andmilitary capability, the unmanned vehicle will not require compliancewith the ITAR controls for items covered under Category VIII of the U.S.Munitions List. Rather, the unmanned vehicle is designed to becontrolled under the Commerce Control List (CCL), such as Export ControlClassification Number (ECCN) 9A012, which covers non-military “unmannedaerial vehicle” (UAV) with Missile Technology (MT) and National Security(NS) reasons for control. An advantage of this feature is that it canexpand commercial use of the vehicle without creating compliance issueswith national security regulations. Many of the techniques used toimplement this feature are directly contrary to features designed intoconventional vehicles and in particular, conventional aircraft. Forexample, typical conventional aircraft are designed to maximize payloadcapacity and/or range while embodiments of the present technology aredesigned to deliberately limit either or both of the foregoing technicalfeatures and/or other technical features.

The computing devices on which the disclosed techniques may beimplemented can include a central processing unit, memory, input devices(e.g., keyboard and pointing devices), output devices (e.g., displaydevices), and storage devices (e.g., disk drives). The memory andstorage devices are computer-readable storage media that may be encodedwith computer-executable instructions that implement the technology,which means a computer-readable storage medium that stores theinstructions. In addition, the instructions, data structures, andmessage structures may be transmitted via a computer-readabletransmission medium, such as a signal on a communications link. Thus,“computer-readable media” includes both computer-readable storage mediafor storing and computer-readable transmission media for transmitting.Additionally, data used by the facility may be encrypted. Variouscommunications links may be used, such as the Internet, a local areanetwork, a wide area network, a point-to-point dial-up connection, acell phone network, wireless networks, and so on.

The disclosed technology may be described in the general context ofcomputer-executable instructions, such as program modules, executed byone or more computers or other devices. Generally, program modulesinclude routines, programs, objects, components, data structures, and soon that perform particular tasks or implement particular abstract datatypes. Typically, the functionality of the program modules may becombined or distributed as desired in various embodiments, includingcloud-based implementations.

Many embodiments of the technology described herein may take the form ofcomputer-executable instructions, including routines executed by aprogrammable computer. Those skilled in the relevant art will appreciatethat aspects of the technology can be practiced on computer systemsother than those shown and described herein. Embodiments of thetechnology may be implemented in and used with various operatingenvironments that include personal computers, server computers, handheldor laptop devices, multiprocessor systems, microprocessor-based systems,programmable consumer electronics, digital cameras, network PCs,minicomputers, mainframe computers, computing environments that includeany of the above systems or devices, and so on. Moreover, the technologycan be embodied in a special-purpose computer or data processor that isspecifically programmed, configured or constructed to perform one ormore of the computer-executable instructions described herein.Accordingly, the terms “computer” or “system” as generally used hereinrefer to any data processor and can include Internet appliances andhand-held devices (including palm-top computers, wearable computers,cellular or mobile phones, multi-processor systems, processor-based orprogrammable consumer electronics, network computers, mini computers andthe like). Information handled by these computers can be presented atany suitable display medium, including a CRT display, LCD, LED display,OLED display, and so on.

The technology can also be practiced in distributed environments, wheretasks or modules are performed by remote processing devices linkedthrough a communications network. In a distributed computingenvironment, program modules or subroutines may be located in local andremote memory storage devices. Aspects of the technology describedherein may be stored or distributed on computer-readable media,including magnetic or optically readable or removable computer disks.Furthermore, aspects of the technology may be distributed electronicallyover networks. Data structures and transmissions of data particular toaspects of the technology are also encompassed within the scope of thetechnology.

FIG. 1 is a block diagram illustrating a control station configured inaccordance with particular embodiments. In this example, the controlstation includes a control station subsystem 110 communicatively-coupledto an antenna interface subsystem 120 and a control GPS interface 130.The control station subsystem 110 includes a video/data exploitationcomputer, a video antenna switch, an uninterruptible power supply (UPS),a trusted platform module, and an interface computer comprising one ormore display screen(s), a keyboard interface, and a multifunctioninterface. The antenna interface subsystem 120, which is communicativelycoupled to a command control and payload control antenna 125, includesan antenna control interface, a command/control transmitter/receiver, avideo receiver, an antenna pointing control interface, and a powerconditioning module. The command control and payload control antenna 125includes frequency feed(s) and antenna pointing actuator(s). The controlGPS interface 130 includes a GPS receiver, a GPS antenna interface, anda subsystem and control interface, and is communicatively coupled to a2-channel GPS antenna 135.

FIG. 2 is a block diagram illustrating subsystems an unmanned aerialvehicle configured in accordance with particular embodiments. In thisexample, the unmanned aerial vehicle includes an avionics subsystem 210communicatively coupled to a left wing subsystem 220, a right wingsubsystem 230, a payload subsystem 240, and a propulsion subsystem 250.The avionics subsystem 210 includes a GPS receiver and antenna, a databus interface, a vehicle/subsystem control interface, a trusted platformmodule, and a mission computer/autopilot comprising airspeed sensors andrate gyros. The left wing subsystem 220 includes a command/controltransmitter/receiver, a video transmitter, and control surfaceactuators. The right wing subsystem 230 includes a video transmitter,and control surface actuators. The payload subsystem 240 includes apayload/turret computer comprising rate gyros and turret axis drives,includes a sensor package comprising a focal plane and a lens assembly,and includes a trusted platform module. The propulsion subsystem 250includes an engine management module, a generator and related interface,a throttle actuator, and a trusted platform module.

FIG. 3 is a block diagram showing some of the components incorporated inassociated computing systems in some embodiments. Computer system 300comprises one or more central processing units (“CPUs”) 301 forexecuting computer programs; a computer memory 302 for storing programsand data while they are being used; a persistent storage device 303,such as a hard drive for persistently storing programs and data; acomputer-readable media drive 304, such as a CD-ROM drive, for readingprograms and data stored on a computer-readable medium; and a networkconnection 305 for connecting the computer system to other computersystems, such as via the Internet. While computer systems configured asdescribed above are suitable used to support the operation of thedisclosed technology, those skilled in the art will appreciate that thetechniques may be implemented using devices of various types andconfigurations. Moreover, communications to and from the CPU and on databuses and lines can be encrypted to protect against snooping of internaldata.

FIG. 4 is a flow diagram illustrating the processing of an “operatevehicle module” configured in accordance with particular embodiments ofthe disclosed technology. The module is invoked to perform vehicleoperations based on an initial specification for a vehicle and thecurrent configuration of the vehicle and its installed components. Inblock 405, the module receives an initial specification for the vehicle.The initial specification may include a list of all components installedon the vehicle and their state or configuration at the time ofinstallation or delivery. For each installed component, thespecification can include an indication of whether the component must bepresent to perform a particular operation. The initial specification maybe encrypted and can be installed by the vehicle manufacturer or anotherparty e.g., an explicitly authorized party. In block 410, the modulereceives a request to operate the vehicle, such as a request to changethe speed of the vehicle, a request to modify a planned route for thevehicle (e.g., add or remove a waypoint from a flight plan), a requestto change the direction of travel of the vehicle, and/or other requests.In block 415, the module identifies those components that must bepresent for the request to be granted by, for example, analyzing theinitial specification. In block 420, the module loops through each ofthe identified components to determine whether they are present andproperly configured. In decision block 425, if the component has alreadybeen selected then processing continues at block 430, else the modulecontinues at decision block 435. In decision block 435, if the selectedcomponent is present, then the module continues at block 440, else themodule continues at block 455. In block 440, the module retrieves thecurrent configuration information for the selected component. Indecision block 445, if the current configuration information for theselected component is different from the configuration informationspecified in the initial specification, then the module loops back toblock 420 to select the next component, else the module continues atdecision block 450. In decision block 450, if the change is acceptablethen the module loops back to block 420 to select the next component,else the module continues at block 455. For example, if the initialspecification indicates that an acceptable payload is 1.4 kg+/−0.2 kgand the payload has changed from 1.3 kg to 1.5 kg, the module willdetermine this change to be acceptable. In this manner, the module candetermine whether a current configuration for a vehicle is consistentwith an initial configuration of the vehicle in determining whether togrant or deny a request. In block 430, the module grants the request,thereby allowing the requested operation to occur and then completesprocessing. In block 455, the module denies the request and thencompletes processing. In some cases, the module may perform additionalactions when denying a request, such as sending out an emergency signal,sending a notification to a ground control station or another vehicle,safely rendering the vehicle inoperable, and so on.

FIGS. 5A-5B illustrate overall views of representative apparatuses andmethods for capturing unmanned aircraft in accordance with embodimentsof the disclosure. Representative embodiments of aircraft launch andcapture techniques are also disclosed in U.S. patent application Ser.No. 11/603,810, filed Nov. 21, 2006, entitled METHODS AND APPARATUSESFOR LAUNCHING UNMANNED AIRCRAFT, INCLUDING RELEASABLY GRIPPING AIRCRAFTDURING LAUNCH AND BREAKING SUBSEQUENT GRIP MOTION (now U.S. Pat. No.7,712,702) and U.S. patent application Ser. No. 13/483,330, filed May30, 2012, entitled LINE CAPTURE DEVICES FOR UNMANNED AIRCRAFT, ANDASSOCIATED SYSTEMS AND METHODS, each of which is herein incorporated byreference in its entirety. Beginning with FIG. 5A, a representativeunmanned aircraft 510 can be captured by an aircraft handling system 500positioned on a support platform 501. In one embodiment, the supportplatform 501 can include a boat, ship, or other water vessel 502. Inother embodiments, the support platform 501 can include otherstructures, including a building, a truck or other land vehicle, or anairborne vehicle, such as a balloon. In many of these embodiments, theaircraft handling system 500 can be configured solely to retrieve theaircraft 510 or, in particular embodiments, it can be configured to bothlaunch and retrieve the aircraft 510. The aircraft 510 can include afuselage 511 and wings 513 (or a blended wing/fuselage), and ispropelled by a propulsion system 512 (e.g., a piston-driven propeller).

Referring now to FIG. 5B, the aircraft handling system 500 can include arecovery system 530 integrated with a launch system 570. In one aspectof this embodiment, the recovery system 530 can include an extendableboom 531 having a plurality of segments 532. The boom 531 can be mountedon a rotatable base 536 or turret for ease of positioning. The segments532 are initially stowed in a nested or telescoping arrangement and arethen deployed to extend outwardly as shown in FIG. 5B. In otherembodiments, the extendable boom 531 can have other arrangements, suchas a scissors arrangement, a parallel linkage arrangement or a knuckleboom arrangement. In any of these embodiments, the extendable boom 531can include a recovery line 533 extended by gravity or other forces. Inone embodiment, the recovery line 533 can include 0.25 inch diameterpolyester rope, and in other embodiments, the recovery line 533 caninclude other materials and/or can have other dimensions (e.g., adiameter of 0.3125 inch). In any of these embodiments, a spring orweight 534 at the end of the recovery line 533 can provide tension inthe recovery line 533. The aircraft handling system 500 can also includea retrieval line 535 connected to the weight 534 to aid in retrievingand controlling the motion of the weight 534 after the aircraft recoveryoperation has been completed. In another embodiment, a differentrecovery line 533 a (shown in dashed lines) can be suspended from oneportion of the boom 531 and can attach to another point on the boom 531,in lieu of the recovery line 533 and the weight 534.

In one aspect of this embodiment, the end of the extendable boom 531 canbe positioned at an elevation E above the local surface (e.g., the watershown in FIG. 5B), and a distance D away from the nearest verticalstructure projecting from the local surface. In one aspect of thisembodiment, the elevation E can be about 15 meters and the distance Dcan be about 10 meters. In other embodiments, E and D can have othervalues, depending upon the particular installation. For example, in oneparticular embodiment, the elevation E can be about 17 meters when theboom 531 is extended, and about 4 meters when the boom 531 is retracted.The distance D can be about 8 meters when the boom 531 is extended, andabout 4 meters when the boom 531 is retracted. In a further particularaspect of this embodiment, the boom 531 can be configured to carry botha vertical load and a lateral load via the recovery line. For example,in one embodiment, the boom 531 can be configured to capture an aircraft510 having a weight of about 30 pounds, and can be configured towithstand a side load of about 400 pounds, corresponding to the force ofthe impact between the aircraft 510 and the recovery line 533 withappropriate factors of safety.

FIG. 6A illustrates a launch system 610 having a launch guide 640 and acarriage 620 that together accelerate and guide an aircraft 650 along aninitial flight path 611 at the outset of a flight. The launch guide 640can include a support structure 641 carrying a first or upper launchmember 642 (e.g., a track) and a second or lower launch member 643, bothof which are generally aligned with the initial flight path 611. Thesupport structure 641 can be mounted to a vehicle (e.g., a trailer or aboat) or to a fixed platform (e.g., a building). Portions of the firstlaunch member 642 and the second launch member 643 can be non-parallelto each other (e.g., they can converge in a direction aligned with theinitial flight path 611) to accelerate the carriage 620, as describedbelow.

The carriage 620 can include a gripper 680 having a pair of gripper arms681 that releasably carry the aircraft 650. The carriage 620 can alsoinclude a first or upper portion 622 and a second or lower portion 623,each of which has rollers 621 (shown in hidden lines in FIG. 6A). Therollers 621 can guide the carriage 620 along the launch members 642, 643while the carriage portions 622, 623 are driven toward each other.Accordingly, normal forces applied to the rollers 621 can drive therollers 621 against the launch members 642, 643, drive the carriageportions 622, 623 together, and drive the carriage 620 forward, therebyaccelerating the aircraft 650 to flight speed.

An actuator 613 can be linked to the carriage 620 to provide thesqueezing force that drives the carriage portions 622, 623 toward eachother and drives the carriage 620 along the launch guide 640. Manyactuators 613 that are configured to release energy fast enough tolaunch the aircraft 650 also have a spring-like behavior. Accordingly,the actuators 613 tend to exert large forces at the beginning of a powerstroke and smaller forces as the power stroke progresses and thecarriage 620 moves along the launch guide 640. An embodiment of thesystem 610 shown in FIG. 6A can compensate for this spring-like behaviorby having a relative angle between the first launch member 642 and thesecond launch member 643 that becomes progressively steeper in thelaunch direction. In one example, the force provided by the actuator 613can decrease from 6000 lbs to 3000 lbs as the carriage 620 accelerates.Over the same distance, the relative slope between the first launchmember 642 and the second launch member 643 can change from 6:1 to 3:1.Accordingly, the resulting thrust imparted to the carriage 620 and theaircraft 650 can remain at least approximately constant.

At or near a launch point L, the carriage 620 reaches the launch speedof the aircraft 650. The first launch member 642 and the second launchmember 643 can diverge (instead of converge) forward of the launch pointL to form a braking ramp 644. At the braking ramp 644, the carriage 620rapidly decelerates to release the aircraft 650. The carriage 620 thenstops and returns to a rest position at least proximate to or coincidentwith the launch position L.

In one embodiment, the actuator 613 includes a piston 614 that moveswithin a cylinder 615. The piston 614 is attached to a flexible,elongated transmission element 616 (e.g., a rope or cable) via a pistonrod 617. The transmission element 616 can pass through a series of guidepulleys 645 (carried by the launch guide 640) and carriage pulleys 624(carried by the carriage 620). The guide pulleys 645 can include firstguide pulleys 645 a on a first side of the support structure 641, andcorresponding second guide pulleys 645 b on a second (opposite) side ofthe support structure 641. The carriage pulleys 624 can also includefirst carriage pulleys 624 a on a first side of the carriage 620 andsecond pulleys 624 b on a second (opposite) side of the carriage 620.One or more equalizing pulleys 646, located in a housing 647 can bepositioned between (a) the first guide pulleys 645 a and the firstcarriage pulleys 624 a on the first side of the support structure 641,and (b) the second guide pulleys 645 b and the second carriage pulleys624 b on the second side of the support structure 641.

In operation, one end of the transmission element 616 can be attached tothe first side of the support structure 641, laced through the firstpulleys 645 a, 624 a, around the equalizing pulley(s) 646, and thenthrough the second pulleys 645 b, 624 b. The opposite end of thetransmission element 616 can be attached to the second side of thesupport structure 641. The equalizing pulley(s) 646 can (a) guide thetransmission element 616 from the first side of the support structure641 to the second side of the support structure 641, and (b) equalizethe tension in the transmission element 616 on the first side of thesupport structure 641 with that on the second side of the supportstructure 641.

When the transmission element 616 is tensioned, it squeezes the carriageportions 622, 623 together, forcing the carriage 620 along theconverging launch members 642, 643. The carriage pulleys 624 and therollers 621 (which can be coaxial with the carriage pulleys 624) aresecured to the carriage 620 so that the carriage 620 rides freely alongthe initial flight path 611 of the aircraft 650 as the carriage portions622, 623 move together.

FIG. 6B illustrates the launch of the carriage 620 in accordance with anembodiment of the disclosure. The carriage 620 is held in place prior tolaunch by a trigger device 639, e.g., a restraining shackle. When thetrigger device 639 is released, the carriage 620 accelerates along thelaunch members 642, 643, moving from a first launch carriage location toa second launch carriage location (e.g., to the launch point L). At thelaunch point L, the carriage 620 achieves its maximum velocity andbegins to decelerate by rolling along the braking ramp 644. In thisembodiment, one or more arresting pulleys 648 can be positioned alongthe braking ramp 644 to intercept the transmission element 616 andfurther decelerate the carriage 620.

As shown in FIG. 6C, once the carriage 620 begins to decelerate alongthe braking ramp 644, the aircraft 650 is released by the gripper arms681. Each gripper arm 681 can include a forward contact portion 682 aand an aft contact portion 682 b configured to releasably engage afuselage 651 of the aircraft 650. Accordingly, each contact portion 682can have a curved shape so as to conform to the curved shape of thefuselage 651. In other embodiments, the gripper arms 681 can engagedifferent portions of the aircraft 650 (e.g., the wings 652). Eachgripper arm 681 can be pivotably coupled to the carriage 620 to rotateabout a pivot axis P. The gripper arms 681 can pivot about the pivotaxes P to slightly over-center positions when engaged with the aircraft650. Accordingly, the gripper arms 681 can securely grip the fuselage651 and resist ambient windloads, gravity, propeller thrust (e.g., themaximum thrust provided to the aircraft 650), and other externaltransitory loads as the carriage 620 accelerates. In one aspect of thisembodiment, each pivot axis P is canted outwardly away from thevertical. As described in greater detail below, this arrangement canprevent interference between the gripper arms 681 and the aircraft 650as the aircraft 650 is launched.

At least a portion of the mass of the gripper arms 681 can be eccentricrelative to the first axis P. As a result, when the carriage 620decelerates, the forward momentum of the gripper arms 681 causes them tofling open by pivoting about the pivot axis P, as indicated by arrows M.The forward momentum of the gripper arms 681 can accordingly overcomethe over-center action described above. As the gripper arms 681 begin toopen, the contact portions 682 a, 682 b begin to disengage from theaircraft 650. In a particular aspect of this embodiment, the gripperarms 681 pivot downwardly and away from the aircraft 650.

From the foregoing, it will be appreciated that specific embodiments ofthe technology have been described herein for purposes of illustration,but that various modifications may be made without deviating from thedisclosure. For example, the unmanned vehicle system can includeadditional components or features, and/or different combinations of thecomponents or features described herein. While particular embodiments ofthe technology were described above in the context of ITAR, MTCR, andEAR regulations, other embodiments using generally similar technologycan be used in the context of other regulations. Such regulations mayvary from one jurisdiction (e.g., national or regional jurisdictions) toanother. Additionally, while advantages associated with certainembodiments of the new technology have been described in the context ofthose embodiments, other embodiments may also exhibit such advantages,and not all embodiments need necessarily exhibit such advantages to fallwithin the scope of the technology. Accordingly, the disclosure andassociated technology can encompass other embodiments not expresslyshown or described herein.

We claim:
 1. A method, performed by a computing system of an unmannedaerial vehicle, for ensuring that the unmanned aerial vehicle complieswith specified export control requirements throughout the operation ofthe unmanned aerial vehicle, the method comprising: storing anindication of an initial specification of the unmanned aerial vehicle,the initial specification of the unmanned aerial vehicle specifyinginitial configuration information and an identification for each of aplurality of tamper-resistant trusted components of the unmanned aerialvehicle, wherein the initial configuration of the unmanned aerialvehicle is in compliance with the specified export control requirementsand wherein at least one of the trusted components is configured toensure that the range of the unmanned aerial vehicle does not exceed apredetermined distance; receiving a request to operate the unmannedaerial vehicle; in response to receiving the request to operate theunmanned aerial vehicle, for each of the plurality of trusted componentsof the unmanned aerial vehicle, querying the trusted component of theunmanned aerial vehicle for current configuration information, whereincommunication with the trusted component of the unmanned aerial vehicleis encrypted, receiving an indication that the trusted component of theunmanned aerial vehicle is not present within the unmanned aerialvehicle or that the configuration of the trusted component of theunmanned aerial vehicle has been modified since the initialspecification was stored, and in response to receiving the indicationthat the trusted component of the unmanned aerial vehicle is not presentwithin the unmanned aerial vehicle or that the configuration of thetrusted component of the unmanned aerial vehicle has been modified sincethe initial specification was stored, modifying the operation of theunmanned aerial vehicle; receiving an indication that the unmannedaerial vehicle is at least a predetermined distance from a launchlocation or that communication between the unmanned aerial vehicle and acontrol station has been lost; and in response to receiving theindication that the unmanned aerial vehicle is at least thepredetermined distance from the launch location or that communicationbetween the unmanned aerial vehicle and the control station has beenlost, modifying a path of the unmanned aerial vehicle.
 2. The method ofclaim 1 wherein at least one of the trusted components of the unmannedaerial vehicle is configured to ensure that a payload of the unmannedaerial vehicle cannot operate when the payload exceeds a predeterminedweight.
 3. The method of claim 1, further comprising: receiving anindication that a speed of the unmanned aerial vehicle is in excess of apredetermined speed threshold; and in response to receiving theindication that the speed of the unmanned aerial vehicle is in excess ofthe predetermined speed threshold, disabling a navigation system of theunmanned aerial vehicle.
 4. The method of claim 1 wherein at least oneof the trusted components of the unmanned aerial vehicle is configuredto ensure that an altitude of the unmanned aerial vehicle exceeds apredetermined altitude threshold while the unmanned aerial vehicle isnot taking off and not landing.
 5. The method of claim 1 whereinmodifying the operation of the unmanned aerial vehicle comprisesdisabling a launch of the unmanned aerial vehicle.
 6. The method ofclaim 1 wherein modifying the operation of the unmanned aerial vehiclecomprises executing a spin-stall maneuver.
 7. The method of claim 1wherein modifying the operation of the unmanned aerial vehicle comprisesdisabling a navigation system of the unmanned aerial vehicle.
 8. Anunmanned vehicle comprising: a memory configured to store initialconfiguration information for each of a plurality of tamper-prooftrusted components of the unmanned aerial vehicle having an initialconfiguration that is in compliance with specified export controlrequirements; and a system verification component configured to, foreach of the trusted components, query the trusted component for currentconfiguration information, receive the current configurationinformation, receive an indication that the current configurationinformation is different from the initial configuration information, anddisable the unmanned aerial vehicle in response to receiving anindication that the current configuration information is different fromthe initial configuration information.
 9. The unmanned vehicle of claim8 wherein at least one of the trusted components is configured to ensurethat a range of the vehicle does not exceed a predetermined distance.10. A computer-readable storage medium storing instructions that, ifexecuted by a computing system, cause the computing system to performoperations comprising: storing an indication of an initial specificationof a vehicle that, at the time of an initial configuration, is incompliance with specified control requirements; receiving a request tooperate the vehicle; and in response to receiving the request to operatethe vehicle, for each of a plurality of trusted components of thevehicle, querying the trusted component of the vehicle for currentconfiguration information, wherein communication with the trustedcomponent of the vehicle is encrypted, receiving an indication that thetrusted component of the vehicle is not present within the vehicle orthat the configuration of the trusted component of the vehicle has beenmodified since the initial specification was stored, and in response toreceiving the indication that the trusted component of the vehicle isnot present within the vehicle or that the configuration of the trustedcomponent of the vehicle has been modified since the initialspecification was stored, denying the request to operate the vehicle.11. The computer-readable storage medium of claim 10 wherein at leastone of the trusted components is configured to ensure that a range ofthe vehicle does not exceed a predetermined distance.
 12. Thecomputer-readable storage medium of claim 10, herein the operationsfurther comprise: in response to receiving the request to operate thevehicle, for each of the plurality of the trusted components of thevehicle, receiving a command from a control station, in response toreceiving the command from the control station, determining that thecontrol station is not a trusted control station, and ignoring thereceived command in response to determining that the control station isnot a trusted control station, and receiving an indication that thevehicle is at least a predetermined distance from a launch location, andin response to receiving the indication that the vehicle is at least thepredetermined distance from the launch location, modifying a path of thevehicle.
 13. The computer-readable storage medium of claim 10, whereinthe operations further comprise: receiving a plurality of points, eachpoint having an associated latitude and longitude; identifying an areadefined by the received plurality of points; and preventing the vehiclefrom traveling outside of the area defined by the received plurality ofpoints.
 14. The computer-readable storage medium of claim 13, whereinthe operations further comprise: receiving an indication that thevehicle is within a predetermined distance from an edge of the areadefined by the received plurality of points; and in response toreceiving the indication that the vehicle is within the predetermineddistance from the edge of the area defined by the received plurality ofpoints, broadcasting an emergency code.
 15. The computer-readablestorage medium of claim 14, wherein at least a first trusted componentof the plurality of trusted components of the vehicle is a softwaremodule and wherein at least a second trusted component of the pluralityof trusted components of the vehicle is a hardware module.
 16. A method,performed by a computing system, for ensuring that an unmanned aerialvehicle complies with specified export control requirements throughoutthe operation of the unmanned aerial vehicle, the method comprising: foreach of a plurality of the export control requirements, determining athreshold value associated with the export control requirement, andinstalling a component on the unmanned aerial vehicle configured toensure that the unmanned aerial vehicle cannot be operated when anattribute of the unmanned aerial vehicle violates the threshold valueassociated with the export control requirement.
 17. The method of claim16 wherein a first export control requirement has an associatedthreshold range value and wherein installing a component for the firstexport control requirement comprises installing a component configuredto ensure that the unmanned aerial vehicle cannot be operated when thedistance of the unmanned aerial vehicle from a launch point exceeds thethreshold range value.